Date: Tue, 14 Jun 2011 00:31:50 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: "Justin T. Gibbs" <gibbs@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r223061 - head/sys/kern Message-ID: <20110613213150.GC48734@deviant.kiev.zoral.com.ua> In-Reply-To: <201106132121.p5DLL2Fp099153@svn.freebsd.org> References: <201106132121.p5DLL2Fp099153@svn.freebsd.org>
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--KCLJDKHmrU6/EDiO Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 13, 2011 at 09:21:02PM +0000, Justin T. Gibbs wrote: > Author: gibbs > Date: Mon Jun 13 21:21:02 2011 > New Revision: 223061 > URL: http://svn.freebsd.org/changeset/base/223061 >=20 > Log: > Fix a couple of race conditions in devstat(9) initialization. > =20 > In devstat_new_entry(), there is no need to initialize the queue > and the mutex in this function. There are ways to do static > initialization on both, so use STAILQ_HEAD_INITIALIZER and > MTX_SYSINIT to initialize the queue and the mutex. > =20 > In devstat_alloc(), use an atomic test and set routine to guard > making our entry in /dev. Using just a plain static variable > creates a race condition on multiprocessor machines. If you > attempt to create a second entry in devfs, the kernel will panic. Devfs returns an error if MAKEDEV_CHECKNAME flag is supplied and attempt is made to create the existing node. The static guard is still useful, since make_dev() call is costly, but you can remove the atomic, since the race should be of limited scope. --KCLJDKHmrU6/EDiO Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (FreeBSD) iEYEARECAAYFAk32gcYACgkQC3+MBN1Mb4j2AwCdG+xcxM5g23Quq4ZSM+zqvkYF BZcAoOWLa7gs2VQMuVGQXU5x3BJwumQF =0ZGG -----END PGP SIGNATURE----- --KCLJDKHmrU6/EDiO--
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